A runway occupancy conflict occurs when an obstruction, e.g., airplane or ground vehicle, is located on a runway during final approach by an airplane that is cleared to land on the runway. If the obstruction located on the ground does not vacate the runway, and the approaching airplane does not abort the final approach, the two vehicles may collide. At a minimum, such a collision can lead to serious damage to or destruction of the airplanes or vehicles involved, and a disruption of the operation of the airport. Such a collision can also lead to the serious injury or death of occupants of the airplanes or vehicles involved.
Air traffic controllers, who direct airplanes and vehicles on the ground and airplanes in the air, are primarily responsible for preventing runway occupancy conflicts. However, air traffic controllers occasionally err by, for example, clearing a first plane to take-off on a runway or taxi across the runway, and clearing a second plane to land on the same runway. Further, pilots occasionally are mistaken as to which runway they have been cleared to taxi across, take off on, or land on. As major hub airports become increasingly large and busy, the potential for air traffic controller and pilot errors of this nature increases. Further, some smaller airports are non-towered, i.e., do not have air traffic controllers.
Even when errors of this nature occur, a collision may be avoided by the pilot on final approach. A pilot on final approach is trained to scan the length of the runway for potential obstructions. If an obstruction is present, the pilot may decide whether to continue with the final approach, call the tower for additional information, and/or abort the final approach and execute a go-around. However, obstructions on the runway may be difficult for pilots to see, especially at night or in poor visibility weather conditions. Further, final approach is a high workload time for pilots, and the level of attention a pilot can devote to scanning the runway may not be adequate in certain situations.